This invention relates to automobile bumpers, in particular to the underlying structural member of a bumper known as a bumper beam.
As is well known, bumpers are attached to the front and rear of vehicles and used for absorbing shock or preventing vehicle damage resulting from a collision. Currently, important considerations underlying the design of vehicle bumpers are: (1) increasing the bumper's capability to withstand impacts while (2) minimizing the weight of the bumper to increase the fuel efficiency of the vehicle to which it is attached.
Past attempts to improve bumpers have resulted in bumpers which do not effectively meet both design goals noted above. Some designs have focused on covering a rigid (usually steel) bumper beam with various energy absorbing devices. See, for example, the patent issued to Montgomery, U.S. Pat. No. 4,061,384. Utilizing a steel bumper beam obviously adds considerable weight to the vehicle, thus reducing vehicle fuel efficiency. Other approaches have been to substitute a molded flexible bumper formed of material such as polypropylene resin for rigid metal bumpers of the past. See, for example, the patent issued to Adachi et al., U.S. Pat. No. 4,504,534. Bumpers formed of such material are lighter in weight than bumpers employing steel beams and have the ability to absorb the energy transmitted by very minor impacts. However, without using an underlying bumper beam having a stiffness, especially in the longitudinal direction, comparable to a metal beam, these latter bumpers cannot withstand substantial impacts.